SAT Question 0d391910: Linear Functions answer and explanation with Desmos solution

Substituting $8$ for $f\left(x\right)$ in the given equation yields $8=4x$. Dividing the left- and right-hand sides of this equation by $4$ yields $x=2$. Therefore, the value of $x$ is $2$ when $f\left(x\right)=8$.